As a result of chromosomal translocation, originally separate genes fuse into a fusion gene. It is known that fusion genes containing part of a kinase gene, such as a BCR-ABL1 fusion in chronic myelogenous leukemia, an EML4-ALK fusion in lung cancer, and an ROS1 fusion in a variety of cancers including lung cancer, often play an essential role in carcinogenesis, and that drugs which inhibit the function become an extremely effective anti-cancer agent (Non-patent literature 1, and patent literatures 1 and 2).
Nowadays, the relationship between molecular diagnosis and therapeutic effects on cancer is being shown clinically by the appearance of, for example, tyrosine kinase inhibitors Iressa and Tarceva. As a result, the concept of drug administration to eligible patients stratified by molecular diagnosis is spreading.
With respect to an ETV6 (Ets Variant6)-NTRK3 (Neutrophic Tyrosine Kinase, Receptor, Type3) fusion, its presence was reported in sarcoma (Non-patent literature 2) and breast carcinoma (Non-patent literature 3), but there has been no report in digestive system cancer. There has been no report that a kinase domain of NTRK3 can be part of a fusion (i.e., the presence of a fusion containing the kinase domain of NTRK3) in digestive system cancer (Non-patent literature 4).